A file server is a computer that provides file service relating to the organization of information on storage devices, such as disks. The file server or filer includes a storage operating system that implements a file system to logically organize the information as a hierarchical structure of directories and files on the disks. Each “on-disk” file may be implemented as a set of data structures, e.g., disk blocks, configured to store information. A directory, conversely, may be implemented as a specially formatted file in which information by other files and directories is stored.
A filer may be further configured to operate according to a client/server model of information delivery to thereby allow many clients to access files stored on a server. In this model, the client may comprise an application, such as a database application, executing on a computer that connects to the filer over a computer network. This computer network could be a point to point link, a shared local area network (LAN), a wide area network (WAN) or a virtual private network (VPN) implemented over a public network such as the Internet. Each client may request the services of the file system on the filer by issuing file system protocol messages (typically in the form of packets) to the filer over the network.
The disk storage typically implemented has one or more storage “volumes” comprised of a collection of physical storage disks, defining an overall logical arrangement of storage space. Currently available filer implementations can serve a large number of discrete volumes (150 or more, for example). Each volume is generally associated with its own file system. The disks within a volume/file system are typically organized as one or more groups of Redundant Array of Independent (or Inexpensive) Disks (RAID). RAID implementations enhance the reliability and integrity of data storage through the redundant writing of data stripes across a given number of physical disks in the RAID group, and the appropriate caching of parity information with respect to the striped data. In the example of a WAFL based file system and process, a RAID 4 implementation is advantageously employed. This implementation specifically entails the striping of data across a group of disks, and separate parity caching within a selected disk of the RAID 4 group.
Each filer is deemed to “own” the disks that comprise the volumes serviced by that filer. This ownership means that the filer is responsible for servicing the data contained on those disks. Only the filer that owns a particular disk should be able to write data to that disk. This solo ownership helps to ensure data integrity and coherency. In prior storage system implementations, it is common for a filer to be connected to a local area network and a fibre channel loop. The fibre channel loop would have a plurality of disks attached thereto. As the filer would be the only device directly connected to the disks via the fibre channel loop, the filer owned the disks on that loop. However, a noted disadvantage of the prior art is the lack of scalability, as there is a limit to a number of disks that may be added to a single fibre channel loop. This limitation prevents a system administrator from having backup filers connected to the disks in the event of failure.
In another prior storage system implementation, two filers, which are utilized as a cluster, could be connected to a single disk drive through the use of the disk's A/B connector. The first filer would be connected to the A connection, while the second filer would be connected to the disk's B connection. In this implementation, the filer connected to a disk's A connection is deemed to own that disk. If the disks are arrayed in a disk shelf, all of the disks contained within that disk shelf share a common connection to the A and B connections. Thus, a filer connected to the A connection of a disk shelf is deemed to own all of the disks in that disk shelf. This lack of granularity (i.e. all disks on a shelf are owned by a single filer) is a known disadvantage with this type of implementation.
FIG. 1 is a schematic block diagram of an exemplary network environment 100. The network 100 is based around a local area network (LAN) 102 interconnection. However, a wide area network (WAN), virtual private network (VPN), or a combination of LAN, WAN and VPM implementations can be established. For the purposes of this description the term LAN should be taken broadly to include any acceptable networking architecture. The LAN interconnects various clients based upon personal computers 104, servers 106 and a network cache 108. Also interconnected to the LAN may be a switch/router 110 that provides a gateway to the well-known Internet 112, thereby enabling various network devices to transmit and receive Internet based information, including e-mail, web content, and the like.
In this implementation, an exemplary filer 114 is connected to the LAN 102. This filer, described further below is a file server configured to control storage of, and access to, data in a set of interconnected storage volumes. The filer is connected to a fibre channel loop 118. A plurality of disks are also connected to this fibre channel loop. These disks comprise the volumes served by the filer. As described further below, each volume is typically organized to include one or more RAID groups of physical storage disks for increased data storage integrity and reliability. As noted above, in one implementation, each disk has an A/B connection. The disk's A connection could be connected to one fibre channel loop while the B connection is connected to a separate loop. This capability can be utilized to generate redundant data pathways to a disk.
Each of the devices attached to the LAN include an appropriate conventional network interface arrangement (not shown) for communicating over the LAN using desired communication protocol such as the well-known Transport Control Protocol/Internet Protocol (TCP/IP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), or Simple Network Management Protocol (SNMP).
One prior implementation of a storage system involves the use of switch zoning. Instead of the filer being directly connected to the fibre channel loop, the filer would be connected to a fibre channel switch, which would then be connected to a plurality of fibre channel loops. Switch zoning is accomplished within the fibre channel switches by manually associating ports of the switch. This association with, and among, the ports would allow a filer connected to a port associated with a port connected to a fibre channel loop containing disks to “see” the disks within that loop. That is, the disks are visible to that port. However, a disadvantage of the switch zoning methodology was that a filer could only see what was within its zone. A zone is defined as all devices that are connected to ports associated with the port to which the filer was connected. Another noted disadvantage of this switch zoning method is that if zoning needs to be modified, an interruption of service occurs as the switches must be taken off-line to modify zoning. Any device attached to one particular zone can only be owned by another device within that zone. It is possible to have multiple filers within a single zone; however, ownership issues then arise as to the disks within that zone.
The need, thus, arises for a technique for a filer to determine which disks it owns other than through a hardware mechanism and zoning contained within a switch. This disk ownership in a networked storage methodology would permit easier scalability of networked storage solutions.
Accordingly, it is an object of the present invention to provide a system and method for implementing disk ownership in a networked storage arrangement.